Vacuum processing machine

ABSTRACT

A VACUUM PROCESSING MACHINE WHEREIN AN EVACUATED ENCLOSURE HOUSES A SERIES OF INTERMESHING TWO-LOBE ROTORS WHICH ARE ALTERNATELY OSCILLATED A HALF-REGOLUTION TO THEREBY CIRCUMFERENTIALLY SHIFT LENTICULAR CARRIER BOATS RECEIVED WITHIN CONCAVE RECESSES BETWEEN THE LOBES TO A TRANSFER POSITION BETWEEN THE ROTORS. THE LOBES OF THE SUCCEEDING ROTORS SWEEP THE RECESSES TO THEREBY SHIFT THE CARRIER BOATS TO THE NEXT ADVANCED TRANSFER POSITION WHEREBY PARTS NESTED ON THE CARRIER BOASTS ARE BIDIRECTIONALLY SHIFTED ALONG A COMMON ENTRANCE AND EXIT PATH IN A SERIES OF ARCS BETWEEN HANDLING AND PROCESSING STATIONS AT OPPOSITE ENDS OF THE ENCLOSURE.

3,714,925 VACUUM PROCESSING MACHINE Eugene C. Helm, Anderson, Ind.,assignor to General Motors Corporation, Detroit, Mich. Filed July 30,1971, Ser. No. 167,566 Int. Cl. C23c 13/10 US. Cl. 11849 1 ClaimABSTRACT OF THE DISCLOSURE A vacuum processing machine wherein anevacuated enclosure houses a series of intermeshing two-lobe rotorswhich are alternately oscillated a half-revolution to therebycircumferentially shift lenticular carrier boats received within concaverecesses between the lobes to a transfer position between the rotors.The lobes of the succeeding rotors sweep the recesses to thereby shiftthe carrier boats to the next advanced transfer position whereby partsnested on the carrier boats are bidirectionally shifted along a commonentrance and exit path in a series of arcs between handling andprocessing stations at opposite ends of the enclosure.

The present invention relates to a machine for transferring articlesand, in particular, to a vacuum processing machine wherein finished andunfinished articles are bidirectionally shifted through a series ofcontrolled environments between handling and processing stations atopposite ends of an evacuated enclosure.

At the present time, large and cumbersome parts such as taillightreflectors pose extremely diflicult problems in subjecting the parts toa high vacuum environment such that a suitable reflective metalliccoating can be applied by vapor deposition. Two methods can generally beemployed for achieving suitable reflectorizing conditions for thesereflectors. In one method, a single reflector is placed in a chamberedfixture which is evacuated until the desired vacuum is reached at whichtime the reflective coating is applied. Thereafter, the chamber isrepressurized and the reflector removed. However, the separate pump downtime required for each article greatly limits the production rate,particularly inasmuch as the pump down time considerably exceeds thecoating time. In the other method, a partial reduction in the pump downtime versus the coating time is achieved by positioning multiplereflectors within a single evacuating chamber and, when the desiredvacuum is reached, sequentially or simultaneously applying a reflectivecoating to the articles. This also is not entirely satisfactory inasmuchas the large volume chamber requires a substantial pump down time whichagain limits the production rate.

The present invention contemplates a continuous vac uum processingmachine for applying a coating to an article wherein the reflectorizingprocess proceeds substantially independently of the system pump downtime. Basically, this improved performance is achieved by continuouslyrouting unfinished parts sequentially through a series of controlledenvironment chambers to a high vacuum processing station for applicationof the coating. Thereafter, the reflectors are reversely routed alongthe same path for exit at the handling or entrance end of the machine.The individual chambers are independently sealed and have progressivelyincreasing vacuums toward the processing station. This provides a vacuumenvironment at the processing station which can be continuouslymaintained and is relatively unaffected by the transferring of parts.

The parts are routed through the machine by a transferring mechanismincluding a series of intermeshing twolobe rotors which operativelycooperate with adjacent rotors and the enclosure to shift articlestoward and away United States Patent pp 3,714,925 Ice Patented Feb. 6,1973 from the processing station. Each rotor includes diametricallyopposed cylindrical lobes which are circumferentially spaced by concavecylindrical recesses. The rotors are spaced on shortened centers and,when the lobes of one rotor are perpendicular to the center line of themachine, the other rotor is freely rotatable and sweeps the cylindricalrecesses. The articles are mounted on lenticular carrier boats havingone cylindrical surface positioned within the recess and the othercylindrical surface forming a continuation of the lobes. Cam drive meansare provided for alternately oscillating alternate rotors or one-halfrevolution. In this manner, the carrier boat is circumferentiallyshifted along an arcuate path by the first rotor for a half revolutionand stopped at a holding position between the rotors. Thereupon, thesecond set of rotors is rotated and the lobes thereof sweep the carrierboats from the first holding positions to second holding positionsbetween the next adjacent rotors. At the other end of the machine duringthe dwelling period of the end rotor, a reflective coating is applied tothe article. During the reverse rotation of the end rotor, the finishedarticle is reversely shifted to the last holding position along itsentrance path. Simultaneously, an unfinished article is shifted from thelast holding position to the processing station along a diametricallyopposite or parallel path. Thus, parts are alternately fed into themachine and bidirectionally carried through a series of controlledenvironments in parallel paths for handling and processing at oppositeends of the machine.

These and other features of the present invention will be apparent toone skilled in the art upon reading the following detailed description,reference being made to the accompanying drawings showing a preferredembodiment in which:

FIG. 1 is a side cross sectional view of a vacuum processing machinemade in accordance of the present invention;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 is an enlarged view taken along line 33 of FIG. 1;

FIG. 4 is an enlarged perspective view of the carrier boat and therotor;

FIG. 5 is an enlarged fragmentary view of the processing station; and

FIG. *6 is a process flow schematic for the vacuum processing machine.

Referring to FIGS. 1 and 2, there is shown a vacuum processing machine10 for applying a reflective coating to articles such as taillightreflectors 11. The machine 10 generally comprises a vacuum enclosure 12supported on legs 14 and having an open entrance or handling station 16at one end and an enclosed processing station 18 at the other end. Theenclosure 12 includes a top wall 20, a bottom wall 22, a pair of spacedside walls 24, and an end wall 26. A series of four intermeshingtwo-lobe rotors 30, 32, 34, 36 are rotatably carried within theenclosure 12. The side walls 24 and the end wall 26 include interiorconcave surfaces conforming to the outer surfaces of the aforementionedrotors.

The rotors 30, 32, 34, 36 respectively include drive shafts 40, 42, 44,46 which are journalled in and project downwardly through openings inthe bottom wall 22. Each drive shaft 40, 42, 44, 46 carries a spur gear50, 52, 54, 56 respectively. Cam drive means 60 are provided foralternately oscillating alternate rotors in a manner described below.

Referring to FIG. 4, the representative rotor 30 comprises planar topand bottom surfaces 61, a pair of diametrically opposed lobes 62 havingright circular peripheral surfaces 63, and a pair of diametricallyopposed concave circular recesses 64 formed normal to the lobes 62.

A sealing strip 68 disposed in a groove around the surfaces 61 and 63cooperates with the wall of the enclosure to a seal between adjacentrotors. As shown in FIG. 2, the rotors are mounted on shortened centersD at a distance equal to the radius of a lobe 62 plus the radius to thebase of the recess 64. With the lobes 62 perpendicular to a longitudinalaxis 70 through the centers of the rotors, each recess 64 forms acircular continuation of the peripheral surface 63 of an adjacent rotor.Additionally, the mutually facing recesses between successive rotorswill establish three holding chambers 72, 74, 76. At the processingstation 18, the rotor 36 and the end wall 26 form a processing cavity78. Therefore, when one set of rotors are located with the lobesperpendicular to the longitudinal axis 70, the adjacent rotors arefreely rotatable with the lobes thereof sweeping the aforementionedrecess 64 and chambers.

Controlled vacuum environments are maintained between adjacent sealingstrips 68 in the chambers 72, 74, 76, 78 by vacuum pumps 80, 82, 84, 86which are respectively connected thereto. The pumps have a capacity tomaintain the chambers at progressively increasing vacuums which is aminimum of around .1 micron in the processing chamber 78. Duringoscillation of the rotors, adjacent pumps jointly evacuate the transientspace between alternate sealing strips 68 thereby minimizing the effectsof the transferring operation on the prevailing environment.

The reflectors 11 are mounted on lenticular carrier boats 90 defined byopposed convex surfaces 92 having a radii equal to the radii of thelobes 62. Accordingly, when the carrier boat 90 is received within arecess 64, one convex surface 92 engages the inner periphery thereof andthe other convex surface forms a circular continuation of the lobes 62.

The carrier boats 90 are bidirectionally shifted through the enclosure12 by the rotors as controlled by the drive means 60 which includesracks 100, 102, a pair of cams 104, 106, and a drive train including anelectric motor 108 operatively coupled to a gear reduction unit 110. Thecams 104, 106 are rotatably mounted on an output shaft 111 connected tothe gear reduction unit 110. Referring to FIG. 3, the representativerack 100 is provided with gear teeth which mesh with the spur gears 52and 54, of rotors 30 and 32. In a similar manner, the rack 102 mesheswith the spur gears 52, 56 of rotors 32, 36. Cam follower pins 112connected at the ends of the racks 100, 102 operatively engage the camsurface 114 of the cams 104, 106.

The profile of each cam includes 90 segments comprising in clockwisecircumferential order a dwell sector A (alpha), a rise sector B (beta),a dwell sector I (gamma), and a fall sector A (delta). The cams 104, 106are circumferentially spaced 90 apart such that one cam is operating ona dwell sector while the other cam operates on an actuating sector. Inthis manner, the cams serve to alternately reciprocate the rack gears100, 102 so as to alternately oscillate their respective rotors withintermediate rest periods.

The processing station 18 is provided with an aluminizer 120 which ismounted on the bottom plate 22 and registers with the cavity 78 throughan aperture 122. The aluminizer 120 includes a crucible 124 which isresistance heated to vaporize aluminum for deposition upwardly throughan opening 126 in the carrier boat 90 onto the interior surface ofreflector 11. The aluminizer is conventional in construction and isappropriately energized during each dwell sector A and I of the endrotor 36.

Referring to FIGS. 2 and 6, in operation unfinished refiectors areshifted along a series of semi-circular paths toward the processingstation 18 while finished reflectors carried by the same rotor arereversely shifted along a parallel path toward the handling station 16.However, with regard to an individual reflector, the identical path isused for ingress and egress. Thus, unfinished and finished parts aretransferred through a series of controlled environments for entrance andexit of one end of the machine and for aluminizing at the other end.

More particularly, upon machine start up, a first or odd numberedcarrier boat is positioned within a recess 64 of the entrance rotor 30.During the rise sector B, the cam 104 drives the rack to the leftthereby rotating rotor 30 one-half revoltion or 180 in thecounterclockwise direction. The intermediate positions of the rotor 30and 34 is shown by phantom lines in FIG. 2. At the same time, the cam'106 is traversing the dwelll sector A and the intermediate rotor 32remains stationary. Accordingly, as shown in FIG. 6, the carrier boat 90is carried on a semi-circular path from the handling station 16 to thefirst holding chamber 72 along a semi-circular circumferential path 130.When the first carrier boat reaches the holding cavity 72, the entrancerotor 30 is locked in place as the cam 104 traverses the dwell sector I.Simultaneously therewith, lthe dam 106 traverses a rise sect-or Bthereby shifting the rack 102 to the left and oscillating theintermediate rotor 32 one-half revolution in a counterclockwisedirection. This movement shifts the first carrier boat in asemi-circular path 132 to the second holding chamber 74.

During the dwell sector I of the rotor 30, a second or even numberedcarrier boat is positioned within the recess 64. As the cam 104traverses the fall sector A (delta), the rack 100 is shifted to theright and the rotor 30 carries the second part, as shown by the dottedlines, in a clockwise direction along a path 134 for deposit at theholding cavity 72 while the intermediate rotor 34 transfers the firstcarrier boat to the holding chamber 76 along a path 136.

During the next 90 sector, the rotors 32 and 36 are driven in aclockwise direction by the fall sector A of the cam 106 and the firstand second carrier boats are transferred to the processing chamber 78and the second holding chamber 74 along paths 138 and 140, respectively.

During the next dwell periods of the rotor 30, 34, the second carrierboat and third carrier boat are transferred to the chambers 76 and 72along paths 142, 130 respectively while the aluminizer is energized forapplying a coating to the reflector 11 on the first carrier boat. Thesecond carrier boat is subsequently transferred to the processingstation 18 along path 144 for aluminizing while the finished odd numberreflector is transferred to the chamber 76 along the path 138.

Regarding unfinished parts, during the next complete revolution the earn104, the first and odd number carrier boats will exit the machine alongtheir entrant path 130, 132, 136 and 138. Similarly, the second and evennumbered reflectors will follow an exiting path identical to theirentrant path 136, 140, 142, 144.

Accordingly, it will be noted that the odd numbered carrier boats willfollow identical paths as they are bidirectionally routed between thehandling station 16 and the processing station -18. The even numberedcarrier boats will move along a path which is parallel to the mirrorimage of the first path. Thus, for each oscillation of the rotors, anunfinished part advances forwardly while a finished part retreats. Inthis manner, reflectors proceed through the machine on a continuousbasis without being dependent on the pump down time of the machine.Accordingly, the production rate for the machine will be substantiallysolely governed by the aluminizing time at the processing station.

Although only one form of this invention has been shown and described,other forms will be readily apparent to those skilled in the art.Therefore, it is not intended to limit the scope of this invention bythe embodiment selected for the purpose of this disclosure but only bythe claim which follows.

What is claimed is:

1. A vacuum processing machine for applying a coating to an article,comprising: an enclosure having a handling station at one end and aprocesisng station at the other end; means for maintaining controlledenvironments at spaced locations along said enclosure; two sets ofalternately spaced two-lobe rotors rotatably mounted within saidenclosure for oscillation between a first transfer position and a secondtransfer position, said rotors having alternating circular lobes andconcave recesses and being spaced on shortened centers such that thelobes of one rotor mesh with and sweep the recess of an adjacent rotorintermediate said transfer positions; sealing means between the rotorsand the enclosure for maintaining said controlled environments; means atsaid processing station for applying a coating to articles positionedtherein; lenticular carrier boats receivable within said recesses havinga first circular surface conforming to said recesses and a secondcircular surface forming a continuation of said lobes; first cam drivemeans for oscillating one set of rotors one-half revolution to therebyadvance carrier boats carrying unfinished articles in a semi-circularpath between successive transfer positions toward the processing stationand return carrier boats carrying finished articles in a parallelsemi-circular path toward the handling station; and second cam drivemeans for oscillating the other References Cited UNITED STATES PATENTS1,774,529 9/1930 Sharp 99-272 2,516,908 8/ 1950 Pottle 118-50 2,730,0681/1956 Reynolds et al. 118-49 3,037,607 6/1962 Hi-ghfield et a1 198-193,656,454 4/ 1972 Schrader 118-49 MORRIS KAPLAN, Primary Examiner US.Cl. X.R. 198-19

